Wavelength division multiplexing (WDM) enables high-speed, large-capacity information communication by carrying optical signals of different optical wavelengths through one optical cable at the same time. A WDM network has multiple optical transmission apparatuses (NEs: Network Elements) such as optical cross-connects (OXCs) connected to each other through communication lines, forming a network of various shapes such as linear shapes, meshes, and rings.
While communication capacity can be expanded by employing a communication mode according to WDM, diversification of services using communication lines causes the utilization states of the communication lines to frequently change. Consequent to a greater volume of data, one service may occupy a larger proportion of the communication routes. In such a situation, to ensure necessary communication routes, multiple optical wavelength paths between optical transmission apparatuses must be set individually without crossing (interference) one another.
Currently, when communication routes are optimized, a maintenance person predicts line utilization states when providing servicing and sets optimal optical wavelength paths. However, if the utilization state is different from the prediction, a central monitoring system (OpS) that manages the network moves optical wavelengths in units of optical wavelength paths.
If optical wavelength paths set in WDM signals are randomly and repeatedly set and deleted, fragmentation of the optical wavelength paths occurs in communication routes. The occurrence of the fragmentation in optical wavelengths makes it difficult to set an optical wavelength path having the same optical wavelength between multiple NEs (long path), reducing usage efficiency of WDM lines.
To avoid such fragmentation, techniques of optimizing the setting of optical wavelength paths have been disclosed (see, e.g., Japanese Laid-Open Patent Publication Nos. 2012-109928 and 2012-195787). In the technique of Japanese Laid-Open Patent Publication No. 2012-109928, the number of used optical wavelength regions is made smaller than that before rearrangement and an available optical wavelength is utilized to change an optical wavelength path to another optical wavelength path. In the technique of Japanese Laid-Open Patent Publication No. 2012-195787, optical wavelengths are rearranged such that optical signals of the same modulation mode become adjacent to one another so as to reduce the number of guard bands having a specific optical wavelength interval on the side portions of the optical signals, thereby increasing the band utilization rate.
However, when the setting of optical wavelength paths is optimized, if the communication routes of the optical wavelength paths are intricately routed in a network of increased scale, rearrangement of the optical wavelength paths without affecting other services is difficult and requires complicated control for execution and high cost for maintenance.
Particularly, no proposal has been made on a method of managing which optical wavelength path is to be rearranged (optimized) or on a technique of efficiently providing control necessary for actual rearrangement (e.g., the number of times an optical wavelength path is moved to a different optical wavelength).